Going again to a different store and playing with it again I have only one criticism.
The only reason for me to buy the camera as a backup to the D90 would be the LCD at waist level (I like the way it's placed for that purpose) with fast Live View for focusing and shooting candids. But it isn't there yet, tho it will be great for setup landscape work.
The Olympus E620 is better for that- faster with less lag time- whatever its other limitations.
For most others tho the D5000 will be great. I agree with all of Mark's positive comments.